Use this calculation to reproduce a defined quantitative method when the observations, units, sampling process, and assumptions match the method shown here.

Treatment event rate

Required number.

Control event rate

Required number.

The cited overview of Number needed to treat supplies background for the terminology and domain context used by this tool.^[1]

Calculate number needed to treat from treatment and control event rates. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Number needed to treat

Returned number.

• A numerical result does not by itself establish data quality, causation, representativeness, independence, distributional fit, or practical significance.
• Treatment event rate must be at least 0.
• Treatment event rate must be no greater than 1.
• Control event rate must be at least 0.
• Control event rate must be no greater than 1.
• Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.

Inspect the underlying data, visualize its distribution, report uncertainty and sample size, and compare the result with a robust or domain-specific method where appropriate.

• Risk Difference Calculator

  Calculate treatment risk minus control risk from event and total counts.

• Relative Risk Calculator

  Calculate relative risk from event and total counts in two groups.

• A/B Test Result Analyzer

  Compare two variant conversion rates with a two-proportion z-test.